Field of the Invention
The present invention relates to a radiation imaging apparatus and a radiation imaging system.
Description of the Related Art
An radiation imaging apparatus performs an imaging operation in synchronism with radiation irradiation by a radiation generation apparatus. Japanese Patent Laid-Open No. 2010-264085 describes a radiation image capturing apparatus that detects radiation irradiation and starts accumulating charges in accordance with the detection. The radiation image capturing apparatus includes a plurality of radiation detection elements arrayed in a matrix, and a plurality of bias lines each connected to the radiation detection elements of a corresponding column. The plurality of bias lines are connected to a connection. The radiation image capturing apparatus includes a current detection means for detecting a current flowing to the connection, and a control means for judging exposure to radiation based on the current detected by the current detection means.
The output of the radiation detection element is decided by the product of the intensity and irradiation time of radiation to irradiate a subject. The radiation irradiation time generally falls within the range of 1 ms to several hundred ms. For example, a portable radiation generator or a radiation generator included in a cart for round visits tends to use a long irradiation time because the radiation output is weak. On the other hand, a stationary radiation generator tends to shorten the irradiation time to prevent image blurs caused by a subject motion. In a case in which radiation irradiation is detected using the integrated value of the bias current, when the integral interval is made long, the time required until detection of radiation irradiation becomes long. Hence, when a subject is irradiated with strong radiation for a short irradiation time, the time from the end of radiation irradiation to detection of radiation irradiation is long, and an artifact readily occurs in an image. On the other hand, with a short integral interval, detection of radiation irradiation may fail if the subject is irradiated with weak radiation for a long irradiation time.